1. Field of the Invention
The present invention relates to an apparatus for regenerating an all-optical signal and method thereof that regenerates a distorted optical signal through regenerating, reamplification, and retiming processes in an optical communication network.
2. Description of the Related Art
Recently, as data traffic increases progressively on the Internet, there has been a demand for a large-capacity wavelength division multiplexing (WDM) optical communication network. It is likely that the response to this need will be a large-capacity optical communication network comprising a long-distance WDM optical transmission network that accommodates high-speed data of 10 to 40 Gb/s per channel, optical cross-connect (OXC), optical add/drop multiplexer (OADM), optical router, etc. In such an optical communication network, a high-speed optical signal of over 10 Gb/s is severely distorted by chromatic dispersion and a non-linear phenomenon produced in an optical fiber, an amplified spontaneous emission (ASE) noise produced from an erbium-doped fiber amplifier (EDFA), and crosstalk, noise, and a non-linear phenomenon produced in an optical node such as the OXC, OADM, and optical router. This distortion causes the production of optical signal amplitude fluctuation, timing jitters, etc.
In order to alleviate the above-described problems, a 3R signal regenerator, which can improve the signal performance by regenerating, reamplifying and retiming the distorted optical signal, is required.
Conventionally, an optical/electronic/optical (O/E/O) 3R signal regenerator, which converts an optical signal into an electric signal, electrically performs the 3R, and then converts the electric signal into an optical signal, has been used. However, this electric 3R type regenerator cannot maintain the transparency that is an inherent characteristic of the optical signal, and has the limitations in processing the basic 3R if the data rate of the wavelength channel becomes high, e.g., about 40 Gb/s.
In order to solve this problem, an all-optical 3R signal regenerator for regenerating a distorted optical signal in an all-optical region has been developed, and apparatuses for regenerating a high-speed return-to-zero (RZ) optical signal of several tens of Gb/s have been published.
However, though the conventional all-optical 3R signal shaper can reshape only the RZ optical signal and thus it can be efficiently used in the OTDM system, it is not suitable for the WDM optical communication network where the non-return-to-zero (NRZ) optical signal is mainly used. Also, in order to perform the retiming operation among the 3R signal regenerating processes, optical clock extraction is required. However this optical clock extraction is a very complicated technique, still presently at an elementary level.